From the Guidelines
This patient with a TSH of 5.66, T3 of 145, and T4 of 0.8 does not require immediate initiation of levothyroxine therapy, as the current evidence suggests that treatment is generally considered for TSH levels greater than 10.0 mIU/L 1. The patient's TSH level is elevated but not to the extent that warrants treatment according to the U.S. Preventive Services Task Force recommendation statement 1.
- The decision to start therapy in patients with TSH levels between 4.5 and 10.0 mIU/L is more controversial, and there is no clinical trial data to support a treatment threshold to improve clinical outcomes 1.
- Given her cardiovascular risk factors, including hypertension, hyperlipidemia, and aortic aneurysm, it is essential to monitor her thyroid function closely, but not to initiate treatment at this time.
- The patient should be advised to have repeat thyroid function tests in 6-12 months to assess for any changes in her thyroid function, as the high variability of TSH secretion levels and the frequency of reversion to normal thyroid function without treatment underscore the importance of not relying on a single abnormal laboratory value as a basis for diagnosis or the decision to start therapy 1.
- It is crucial to consider the potential harms of overdiagnosis and overtreatment, particularly because the disorder is defined by silent biochemical parameters rather than a set of reliable and consistent clinical symptoms 1.
From the Research
Patient Profile
- 46-year-old female with a history of hypertension (HTN), hyperlipidemia (HLD), and a newly found aortic aneurysm
- Presents to primary care office with the following lab results: TSH of 5.66, T3 of 145, and T4 of 0.8
Hypothyroidism Treatment
- Levothyroxine is the standard therapy for patients with hypothyroidism, as stated in the study by 2
- The initial dosing of levothyroxine can vary greatly and may be based on the amount of residual thyroid function retained by the patient, body weight or lean body mass, and thyroid-stimulating hormone levels
- A full starting dose of levothyroxine in cardiac asymptomatic patients with primary hypothyroidism is safe and may be more convenient and cost-effective than a low starting dose regimen, as shown in the study by 3
Levothyroxine Dose Adjustment
- Optimal treatment of hypothyroidism requires a partnership between patient and physician, with the physician tasked with vigilant appraisal of the patient's status and appropriate adjustment of their levothyroxine therapy, as stated in the study by 2
- Many levothyroxine preparations have relatively large intervals between tablet strengths at the lower end of their dose ranges, which may represent a barrier to achieving the optimum maintenance treatment for some patients, as mentioned in the study by 4
- The availability of intermediate tablet strengths of levothyroxine in the 25-75 μg range may facilitate precise and effective dose titration of levothyroxine, as suggested in the study by 4
Cardiovascular Disease Risk
- Subclinical hypothyroidism has been associated with risk factors for cardiovascular disease, such as hypertension and dyslipidemia, as stated in the study by 5
- The use of levothyroxine in subclinical hypothyroidism to reduce cardiovascular disease risk is not clearly beneficial, and treatment decisions should be individualized based on patient age, degree of serum thyroid-stimulating hormone elevation, symptoms, cardiovascular disease risk, and other co-morbidities, as recommended in the study by 5
- The use of liothyronine (LT3) with or without levothyroxine (LT4) may be associated with increased incidence of heart failure and stroke, especially in patients with a longer duration of LT3 use and history of thyroid cancer, as shown in the study by 6